Autofocus camera systems and methods

ABSTRACT

A method for focusing a miniature camera includes providing a current through a coil, moving a lens of a camera based on the current to adjust a focus of the camera, and limiting movement of the lens along an optical path of the camera.

PRIORITY CLAIM

This application is a continuation of application Ser. No. 13/225,257filed Sep. 2, 2011, which is a continuation of Ser. No. 12/873,943 filedSep. 1, 2010, now U.S. Pat. No. 8,014,662 issued Sep. 6, 2011, which isa divisional of application Ser. No. 11/361,608 filed Feb. 24, 2006, nowU.S. Pat. No. 7,813,634 issued Oct. 12, 2010, which is acontinuation-in-part of both application Ser. No. 11/268,849 filed onNov. 8, 2005, now U.S. Pat. No. 7,646,969 issued Jan. 12, 2010, andapplication Ser. No. 11/269,304 filed Nov. 8, 2005, now U.S. Pat. No.7,555,210 issued Jun. 30, 2009, both of which claim priority to andbenefit of U.S. Provisional Patent Application No. 60/657,261 filed Feb.28, 2005. The respective disclosures of each of these references isincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates generally to cameras. The presentinvention relates more particularly to a miniature autofocus camera thatis suitable for use in personal electronic devices, such as cellulartelephones.

BACKGROUND

Digital cameras are well known. As their cost drops, digital camerascontinue to grow in popularity. Digital cameras eliminate the need topurchase film and have it developed. They also greatly reduce the needto have prints made, since digital images can easily be viewed on acomputer monitor or the like. Digital cameras have thus reduced theoverall cost of photography.

One rapidly growing application for digital cameras is their use inpersonal electronic devices, such as cellular telephones. Camera phonesoutsold other digital cameras for the first time in the last quarter of2003. Camera phones enable pictures to be conveniently and rapidlyshared with others. Images can be captured on the spur of the moment andthen easily communicated to others via the cellular telephone networkand/or via the Internet.

Although such contemporary camera phones have proven generally suitablefor their intended purposes, they possess inherent deficiencies thatdetract from their overall effectiveness and desirability. For example,contemporary digital cameras commonly have variable focus. However,contemporary camera phones do not have this desirable feature.Contemporary variable focus mechanisms are simply too bulky for today'scompact camera phones.

Consequently, contemporary camera phones have fixed focuses. Although afixed focus can sometimes be adequate under good lighting conditions, afixed focus generally does not perform well when the camera is used inlow light conditions. A fixed focus mechanism approximates a pinholelens to provide sufficient depth of field so as to remain in focus, atleast to some degree, regardless of the distance between the subject andthe camera. However, such a stopped-down lens is undesirably sensitiveto ambient lighting conditions. This is because the near pinhole lens ofa fixed focus camera does not admit much light. Thus, such fixed focuscameras generally require more light than variable focus cameras. Inaddition, the small aperture of a pinhole lens limits the resolution ofthe camera, due to the diffraction limit of light. Thus, such fixedfocus cameras generally have lower resolution than variable focuscameras.

When there is insufficient ambient lighting, the image tends to appearundesirably dark. In recognizing the limitations of contemporary cameraphones using such fixed focus lenses, the prior art has provided flashmechanisms in an attempt to insure that adequate light is provided.However, cellular telephones use battery power supplies, and thus havelimited power available for the use of such flash mechanisms. Morefrequent use of the flash to take photographs thus results in the needto more frequently charge the camera phone. Of course, frequentrecharging is undesirable.

As such, it is desirable to provide a miniature autofocus camera that issuitable for use in personal electronic devices, such as cellulartelephones.

BRIEF SUMMARY

Systems and methods are disclosed herein to provide a miniatureautofocus camera that is suitable for use in personal electronicdevices, such as cellular telephones, pocket PCs, notebook computers,laptop computers, and tablet computers. In accordance with an embodimentof the present invention, a stage for a miniature camera is at leastpartially formed by a MEMS process. The stage can comprise a fixedportion, a movable portion, and flexures for controlling movement of themovable portion with respect to the fixed portion. Thus, for example, alens can be attached to the movable portion of the MEMS stage andmovement of the lens can be substantially limited to movement in onedegree of freedom.

In one example embodiment, a method for focusing a miniature cameraincludes effecting a current flow through a coil, moving a magnet inresponse to the current flow, moving a MEMS stage in response to themoving of the magnet, moving a lens in response to the moving of theMEMS stage, and limiting movement of the MEMS stage to substantially onedegree of freedom.

In another embodiment, a method for making a photograph compriseseffecting current flow through a coil, moving a lens in response to thecurrent flow, limiting movement of the lens to substantially one degreeof freedom along an optical axis of the lens with a snubber assembly,and focusing an image on an imaging sensor in response to the moving ofthe lens.

According to another embodiment, a method for operating an electronicdevice comprises using a controller to control a Lorentz actuator suchthat a lens which is limited to a single degree of freedom of movementby a snubber assembly focuses an image on an imaging sensor.

According to an embodiment of the present invention, a stage assemblycan comprise a stage, at least one magnet of an actuator attached to thestage for effecting movement of the stage, and at least one lensattached to the stage such that movement of the lens effects focusing ofthe camera. A coil attached to a housing of the camera can cooperatewith the magnet to effect such movement.

Thus, according to an embodiment of the present invention, a method forfocusing a miniature camera can comprise effecting current flow througha coil such that a magnet moves in response to the current flow. A stagemoves in response to movement of the magnet and a lens moves in responseto movement of the stage.

According to an embodiment of the present invention, a method forassembling a miniature camera can comprise attaching a magnet assembly,a stage, and a lens mount together in a planar fashion. Such assemblyfacilitates the use of automated assembly equipment, such as pick andplace equipment.

According to an embodiment of the present invention, a miniature cameracan comprise a housing and a coil attached to the housing so as to besubstantially fixed in position with respect thereto. The housing can beconfigured so as to align the coil with respect to a magnet attached toa stage. The housing can also be configured so as to align the stagewith respect to an imaging sensor.

According to an embodiment of the present invention, a miniature cameracan comprise an imaging sensor, a lens mount configured to mount atleast one lens, and a cover within which the lens mount is disposed. Thecover and the lens mount can be configured so as to limit movement ofthe lens mount. For example, the cover can be configured so as to abutthe lens mount when the lens mount moves to a limit of travel away fromthe imaging sensor.

The cover can be formed of metal and configured so as to mitigateelectromagnetic interference with the camera. Thus, performance of thecamera can be substantially enhanced.

According to an embodiment of the present invention, a miniature cameracan comprise an imaging sensor, an optics assembly having at least onemovable optical element wherein movement of the optical element(s)effect focusing of the camera, a MEMS stage to which the movable opticalelement(s) are attached such that the stage controls motion of themovable optical element(s), and an actuator for moving the stage.

According to an embodiment of the present invention, a miniature cameracan comprise an imaging sensor, a housing, and a MEMS stage disposedwithin the housing, wherein the MEMS stage is configured so as to movesubstantially in only one degree of freedom. A snubber assembly can beconfigured to further limit movement of the MEMS stage in substantiallyfive degrees of freedom, so as to protect the stage from excessivemovement. A lens holder can be attached to one surface, e.g., the uppersurface, of the stage. At least one focusing lens can be attached to thelens holder.

An actuator can be disposed within the housing. The actuator cancomprise a coil attached to the housing and a magnet attached to thestage. The housing can align the coil with respect to the magnet and canalso align the stage with respect to the imaging sensor. A bias springcan be configured to bias the stage into a predefined position withrespect to the housing. The metal cover can be configured tosubstantially enclose the actuator and the imaging sensor. The actuatorcan effect movement of the lens so as to provide desired focusing of animage upon the imaging sensor.

According to an embodiment of the present invention, a method for makinga miniature camera can comprise providing a printed circuit board,attaching an imaging sensor to the printed circuit board, providing aMEMS stage that is configured to move in substantially only one degreeof freedom, attaching a lens mount to the MEMS stage in a planarfashion, attaching a lens to the lens mount, attaching a magnet to theMEMS stage in a planar fashion, providing a housing, attaching a coil tothe housing, placing the MEMS stage and a snubber assembly within thehousing, wherein the snubber assembly is configured to limit movement ofthe MEMS stage in substantially five degrees of freedom, compressing abias spring so as to bias the stage into a predefined position withrespect to the housing and attaching a clip to the housing so as to holdthe bias spring in place, and at least partially enclosing the actuatorand the imaging sensor with a metal cover.

In view of the foregoing, a miniature autofocus camera is provided. Theminiature autofocus camera is suitable for use in personal electronicdevices, such as cellular telephones. The autofocus miniature camera canprovide enhanced images in low light conditions. The need for a flash ismitigated, such that battery life is extended.

This invention will be more fully understood in conjunction with thefollowing detailed description taken together with the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an autofocus camera according to anexemplary embodiment of the present invention, wherein anelectromagnetic interference (EMI) shield of the camera has been omittedto better show components thereof;

FIG. 2 is an exploded view of the autofocus camera of FIG. 1, includingthe electromagnetic interference shield thereof;

FIG. 3 is a pictorial flow chart showing assembly of the autofocuscamera of FIG. 1, according to an exemplary embodiment of the presentinvention;

FIG. 4 is an enlarged perspective view of the stage and snubber assemblyof FIG. 2;

FIG. 5 is an exploded perspective view of the stage and snubber assemblyof FIG. 4;

FIG. 6 is an enlarged side view of the magnet assembly of FIG. 2;

FIG. 7 is a perspective top view of the magnet assembly of FIG. 6;

FIG. 8 is a perspective bottom view of the magnet assembly of FIG. 6;

FIG. 9 is a perspective view of the housing of FIG. 2, including theactuator coil;

FIG. 10 is a is a perspective view of the magnet assembly of FIG. 8attached to the bottom of the stage and snubber assembly of FIG. 4;

FIG. 11 is a perspective view of the magnet assembly of FIG. 8 attachedto the bottom of the stage and snubber assembly of FIG. 4 and the lensmount of FIG. 2 attached to the top thereof;

FIG. 12 is a perspective view of the lens mount, magnet assembly, andthe stage and snubber assembly (attached to one another) as they arebeing inserted into the housing of FIG. 2;

FIG. 13 is a perspective view of the lens mount, magnet assembly, andthe stage and snubber assembly after they have been inserted into thehousing of FIG. 2, and showing the clip of FIG. 2 as it is beingattached to the housing so as to maintain the bias spring therein;

FIG. 14 is a perspective view of the lens mount, magnet assembly, andthe stage and snubber assembly after they have been inserted into thehousing of FIG. 13, and showing the clip after it has been attached tothe housing;

FIG. 15 is a perspective view of the partially assembled autofocuscamera of FIG. 14 after the lens assembly of FIG. 2 has been screwedinto the lens mount thereof;

FIG. 16 is an enlarged front view of the printed circuit board of FIG.2.

FIG. 17 is a front view of the printed circuit board of FIG. 16 havingthe partially assembled autofocus camera of FIG. 14 attached thereto,wherein the lens assembly is removed to show the imaging sensor attachedto the printed circuit board; and

FIG. 18 is a perspective view of the assembled autofocus camera of FIG.2.

Embodiments of the present invention and their advantages are bestunderstood by referring to the detailed description that follows. Itshould be appreciated that like reference numerals are used to identifylike elements illustrated in one or more of the figures.

DETAILED DESCRIPTION

When an optical system is reduced in size, the precision required forthe placement of optical elements has to be improved in proportion tothe reduction in size. In other words, optical systems can scale in sizelinearly. For cameras in cellular telephones, the reduction in the sizeof the imaging system can be dramatic. It is thus a challenge to be ableto position and move the optical elements with respect to each otherwith the required precision.

To be able to accomplish autofocus in a cellular telephone camera, it iscommon to move a lens or group of lenses. The position and motion ofthese lenses has to be very precise. Achieving such precision usingcontemporary technologies is difficult.

One or more embodiments of the present invention provide enhancedprecision in the motion of very small camera components by using a microelectromechanical systems (MEMS) stage. This MEMS stage provides forvery precise control in the motion of a lens and accomplishes this in asuitably compact form. The MEMS stage serves as an optical bench forprecision alignment of the lens with respect to an imaging sensor.According to an embodiment of the present invention, the MEMS stagemoves substantially within a plane. That is, the stage tends to remainwithin the plane defined by the stage itself, rather than movingsubstantially orthogonally to this plane.

The MEMS stage can be moved by using an electromagnetic actuator. Amagnet assembly part of the actuator can be attached to one side, e.g.,the bottom, of the stage. A coil of the actuator can be attached to ahousing of the camera. The coil and the magnet assembly are aligned toeach other via the MEMS stage and the housing. A lens mount that holdsthe optical element can be attached to the other side, i.e., the top, ofthe stage. To control the alignment, e.g., tilt, of the lens(es) withrespect to an imaging sensor, a number of features are introduced so asto passively align optical components with respect to each other.

Thus, a method and system for providing an autofocus camera aredisclosed herein. According to one embodiment of the present invention,the autofocus camera is a miniature camera that is suitable for use inpersonal electronic devices, such as cellular telephones, pocket PCs,notebook computers, laptop computers, and tablet computers. At least oneembodiment of the autofocus camera of the present invention is alsosuitable for use as a stand alone device. Such a stand alone device canbe used for security and surveillance applications, as well as any otherdesired applications.

The MEMS stage can be used to control the motion of a lens so that thelens moves substantially in only one degree of freedom. The magnetassembly and the lens mount can be attached to the MEMS stage in aplanar fashion, so as to better facilitate the use of automated assemblyequipment. The housing can be configured so as to both hold the coil ofan actuator and align the coil with respect to a magnet assembly. Thehousing can also be configured so as to align the MEMS stage (andtherefore the lens) with respect to the imaging sensor.

Attaching one component to another in a planar fashion as referred toherein can mean placing one component atop another component. Thus,assembling components in a planar fashion can be stacking of thecomponents.

A bias spring can be used to position the stage such that the lens ispositioned for focus at one extreme of its travel, e.g., at infinity,when no power is applied to the actuator. Bias spring can be formed of anon-magnetic material so as not to interfere with operation of theactuator. A simple metal clip can be used to hold the bias spring inposition against the magnet assembly (which can be attached to thestage).

A metal cover can be used both for electromagnetic interference (EMI)protection and for limiting the motion of the lens mount, The lens mountcan have a visor like structure that is configured to abut the metalcover when the stage (and consequently the lens mount) moves too far onedirection, e.g., away from the imaging sensor. The visor like structurecan be configured so as to abut against the housing when the stage (andconsequently the lens mount) moves too far in the other direction, e.g.,toward the imaging sensor.

The MEMS stage motion can be limited in all degrees of freedom bysnubbers so as to protect the flexures from over extending and/or overcompressing, such as during a shock. In the travel direction (adirection along an optical axis of the camera in which one or morelenses move to effect focusing), the lens mount can abut axial snubbersto limit the motion. In all other degrees of freedom, the silicon stageabuts with six degree of freedom snubbers if the stage's normal limitsof motion are exceeded.

These, as well as other features and aspects of various exemplaryembodiments of the present invention are discussed below in furtherdetail with respect to the drawings.

Referring now to FIGS. 1 and 2, according to one embodiment of thepresent invention, a miniature autofocus camera can comprise a cameraassembly 10 mounted upon a printed circuit board (PCB) 11. Cameraassembly 10 can comprise camera optics 12. Camera optics 12 can have atleast one movable optical element, such as a lens, so as to facilitatefocusing of an image upon an imaging sensor 13.

Imaging sensor 13 can be mounted to printed circuit board 11.Alternatively, imaging sensor 13 can be attached to camera assembly 10.Attachment of imaging sensor 13 to printed circuit board 11 facilitatescommunication of electrical signals between imaging sensor 13 and otherelectrical components such as a monitor, memory, and/or a processor. Forexample, such electrical communication can be facilitated by conductivetraces formed upon printed circuit board 11.

As discussed in further detail below, camera optics 12 can be attachedto a stage assembly 14 that controls movement of camera optics 12.Movement of camera optics 12 is controlled in a manner that facilitatesfocusing of the miniature camera while also mitigating misalignment ofthe optical elements of the miniature camera. Thus, linear movement ofcamera optics 12 along an optical axis of the camera, e.g., toward andaway from imaging sensor 13, is facilitated while movement perpendicularto the optical axis and all rotation of camera optics 12 is inhibited.

More particularly, a stage 401 (better shown in FIGS. 4 and 5) isconfigured so as to facilitate movement along the direction of theoptical axis while not readily facilitating other movement. A six degreeof freedom snubber 402 cooperates with axial snubbers 403 to limitmovement of stage 401 beyond that for which it is configured.Construction and operation of stage 401, six degree of freedom snubbers402, and axial snubbers is discussed in further detail below.

A magnet assembly 16 and coil 17 cooperate to define an actuator thateffects movement of a stage 401 (and consequently camera optics 12)along the optical axis of the miniature camera to facilitate focusing.The actuator can be a Lorentz actuator. Alternatively, the actuator canbe any other desired type of actuator. Advantages associated with theuse of the particular Lorentz actuator disclosed herein include smallsize, reduced weight, low profile, and strong forces generated thereby.Such an actuator is discussed in further detail in commonly ownedapplication Ser. No. 11/263,149, filed on Oct. 31, 2005, and entitledLORENTZ ACTUATOR FOR MINIATURE CAMERA, the disclosure of which isincorporated herein by reference.

Magnet assembly 16 can be attached to the underside of stage assembly 14and coil 17 can be attached to housing 20. Housing 20 generally enclosescamera optics 12, stage assembly 14, magnet assembly 16, and coil 17.Housing 20 also facilitates attachment of camera assembly 10 to printedcircuit board 11, such as via the use of adhesive bonding. Housing 20can alternatively be attached to printed circuit board 11 via the use ofdetents, fasteners, ultrasonic welding, soldering, or via any otherdesired method.

An electromagnetic interference shield 22 can optionally cover asubstantial portion of the miniature autofocus camera of the presentinvention so as to mitigate the undesirable effects of electromagneticinterference thereupon. As those skilled in the art will appreciate, asminiature cameras get smaller, the effects of electromagneticinterference tend to become more pronounced. As miniature cameras getsmaller, the amount of current and voltage used in control and imagesignals tends to be reduced. The use of lower signal levels potentiallymakes these signals more susceptible to interference, such as thatcaused by electromagnetic radiation emitted by nearby electronicdevices, as well as possibly by the personal electronic device withinwhich the miniature camera is installed itself.

A transparent window 23 can be attached to electromagnetic interferenceshield 22. Electromagnetic interference shield 22 and window 23 cancooperate to inhibit environment contaminants, such as dust, moisture,and smoke, from undesirably contacting optical elements of the miniaturecamera, such as the lens(es) of camera optics 12 and such as imagingsensor 13. Electromagnetic interference shield 22 can also define a stopthat at least partially defines one or more limits on the motion ofcamera optics 12, as discussed below.

Clip 24 holds bias spring 25 in place. Bias spring 25 biases stageassembly 14 in one direction of its travel, e.g., at a position forfocus at infinity. Such biasing provides a known starting position ofstage assembly 14 to better facilitate control of movement thereof andprovides a desirable failsafe (focus at infinity) therefore. Such a biasspring is discussed in further detail in application Ser. No.11/219,259, filed Sep. 2, 2005, and entitled MINIATURE CAMERA BIASSPRING, the disclosure of which is incorporated herein by reference.

Contacts 26 facilitate electrical communication between coil 17 andprinted circuit board 11. Each of two leads of coil 17 can be inelectrical communication with a dedicated contact 26. Each contact 26can contact a conductive pad of printed circuit board 11. However, thoseskilled in the art will appreciate that other means for facilitatingelectrical communication between coil 17 and printed circuit board 11are likewise suitable.

Referring now to FIG. 3, a flow chart showing assembly of the autofocuscamera of FIG. 1 according to an exemplary embodiment of the presentinvention is provided. Steps 3142 are some key aspects of the assemblyof the autofocus camera.

According to an embodiment of the present invention, the autofocuscamera can be assembled by providing stage assembly 14 and magnetassembly 16 as shown in step 31 and attaching them together, such as viaadhesive bonding, to form stage and magnet assembly 50 as shown in step32. Lens mount 111 can then be attached, such as via adhesive bonding,to the stage and magnet assembly 50 to provide the lens mount assembly51 shown in step 33.

Lens mount 111, stage assembly 14, and magnet assembly 16 can beassembled to one another in a planar fashion. That is, lens mount 111,stage assembly 14, and magnet assembly 16 can be assembled to oneanother by successively placing one item atop another. Such assemblyfacilitates the use of automated assembly equipment such as robots orpick and place equipment. For example, such automated assembly equipmentcan apply adhesive to magnet assembly 16, place stage assembly 14 uponmagnet assembly 16, apply adhesive to stage assembly 14, and place lensmount 111 upon stage assembly 14.

Housing 22 and lens mount assembly 51 of step 34 can be assembledtogether by inserting lens mount assembly 51 into housing 22 to providemodule assembly 52 of step 35. Insertion of lens mount assembly 51 intohousing 22 can be performed using automated assembly equipment.

Optionally, oil can be applied to stage assembly 14 to provide damping.The application of oil to stage assembly 14 can be performed prior toinsertion of lens mount assembly 51 into housing 22. The oil can beapplied between stage 401 (FIG. 5) and six degree of freedom snubber402. Such damping can enhance operation of the autofocus camera bysmoothing the movement of the stage 401. Such damping can also provideenhanced protection against vibration and shock. Such oil damping isdiscussed in further detail in application Ser. No. 11/219,137, filedSep. 1, 2005 and entitled OIL DAMPING FOR CAMERA OPTICAL ASSEMBLY, thedisclosure of which is incorporated herein by reference. In otherembodiments, oil may not be added to the MEMS stage.

Lens holder 112 can be attached to lens mount 111 of module assembly 52to provide lens assembly 53 of step 36. Then, bias spring 25 and clip 24can be attached to lens assembly 53 as shown in steps 37 and 38.

Functional testing can be performed in step 38 to assure properoperation of the miniature autofocus camera. Functional testing can beperformed using test equipment that effects functioning of the autofocusmechanisms such as the actuator defined by magnet assembly 16 and coil17. Such functional testing can verify proper operation of stageassembly 14, such as the motion control aspects thereof.

Lens assembly 53 can be attached to a printed circuit board 11 at step39. The focus can be tested to provide a focus score at step 40. Focustesting can be performed using modulation transfer function (MTF). Thoseunits that do not achieve a focus score above a predetermined value canbe re-worked and/or rejected. Electromagnetic interference shield 11 canbe added at step 42 and then additional testing can be done.

Some aspects of the assembly steps shown in FIG. 3 are discussed infurther detail below. Those skilled in the art will appreciate thatother sequences of operations can be used to assemble the autofocuscamera of one or more embodiments of the present invention.

Referring now to FIGS. 4 and 5, a stage assembly 14 comprises a stage401, a six degree of freedom snubber 402 within which stage 401 iscaptured, and axial snubbers 403. Six degree of freedom snubber 402 cancomprise an upper portion 411 and a lower portion 412 that cooperate tosandwich stage 401 therebetween. Six degree of freedom. snubber 402 canbe formed of a rigid polymer material.

Axial snubbers 403 can be formed integrally with upper portion 411 ofsix degree of freedom snubber 402. Alternatively, axial snubbers 403 canbe formed separately from upper portion 411 of six degree of freedomsnubber 402 and then attached thereto.

Stage 401, in cooperation with six degree of freedom snubber 402 andaxial snubbers 403, defines the motion of camera optics 12. That is,stage 401 and six degree of freedom snubber 402 enable substantialmovement of camera optics 12 along an optical axis of the autofocuscamera, e.g., in the directions of double-headed arrow 406, whilelimiting both translation and rotation about all other axes. A width ofstage 401 can be defined as being the shortest of the two longerdimensions thereof, such as the dimension in the direction of arrow 406.A length of stage 401 can be defined as being the longest of the twolonger dimensions thereof, such as the dimension perpendicular to thedirection of arrow 406. A height of stage 401 can be defined as beingthe shortest dimension of stage 401 (i.e., from a top or upper surfacethereof to a bottom or lower surface thereof as shown in FIG. 4).

Flexures 404 extend from a stationary portion of stage 401 to a movingportion thereof. Flexures 404 facilitate movement of stage 401 along theoptical axis while tending to inhibit other movement thereof. Furtherdisclosure regarding such flexures is provided in U.S. Pat. No.6,850,675, issued Feb. 1, 2005, and entitled BASE, PAYLOAD ANDCONNECTING STRUCTURE AND METHODS OF MAKING THE SAME; application Ser.No. 11/041,122, filed Jan. 21, 2005, now U.S. Pat. No. 7,266,272, issuedSep. 4, 2007, and entitled MOTION CONTROL STAGES AND METHODS OF MAKINGTHE SAME; and application Ser. No. 11/037,883, filed Jan. 18, 2005, nowU.S. Pat. No. 7,113,688, issued Sep. 26, 2006, and entitled BASE,PAYLOAD AND CONNECTING STRUCTURE AND METHODS OF MAKING THE SAME. Therespective disclosures of each of these patents is incorporated hereinby reference.

Six degree of freedom snubber 402 prevents stage 401 from movingsubstantially beyond the range of motion permitted by flexures 404. Inthis manner, six degree of freedom snubber mitigates the likelihood ofincurring damage to flexures 404, stage 401, and/or other cameracomponents due to excessive motion of stage 401, such as due toexcessive translation and/or rotation thereof. Such a six degree offreedom snubber is discussed in further detail in Application Ser. No.11/268,849, filed Nov. 8, 2005, now U.S. Pat. No. 7,646,969, issued Jan.12, 2010, and entitled CAMERA SNUBBER ASSEMBLY, the disclosure of whichis incorporated herein by reference.

Axial snubbers 403 limit movement of camera optics 12 (FIG. 2) along thedirection of double-headed arrow 406. Axial snubbers 403 thus also limitmovement of stage 401 within six degree of freedom snubber 402. Axialsnubbers 403 limit movement of lens mount 111 (and consequently of lensholder 112, stage 401, and magnet assembly 16 as well) by abutting stop415 of lens mount 111 that is disposed in gap defined by adjacent axialsnubber 403, as best seen in FIG. 11. Thus, as lens mount 111 movesalong the optical axis defined by double-headed arrow 406, stops 415contacts axial snubber 403 when it travels to each extreme of itsmovement.

Axial snubbers can be formed of a polymer material, such as siliconrubber, to cushion such contact. It should be noted that the camera canbe configured such that contact of stops 415 with axial snubbers doesnot occur during normal operation. Such limiting of the movement ofcamera optics 12 and stage 401 can mitigate the likelihood of damage tocamera optics 12, stage 401, flexures 404, six degree of freedom snubber402, and other miniature camera components during abnormal events, suchas shock. Such axial snubbers 403 are discussed in further detail inapplication Ser. No. 11/269,304, filed Nov. 8, 2005, now U.S. Pat. No.7,555,210, issued Jun. 30, 2009, and entitled AXIAL SNUBBERS FOR CAMERA,the disclosure of which is incorporated herein by reference.

Stage 401 can be formed of silicon using micro electromechanical systems(MEMS) techniques. For example, stage 401 can be formed by etching ormicromachining silicon. The fixed portion of stage 401, the movingportion of stage 401, and flexures 404 can be formed from a single,monolithic piece of material, such as silicon. Micromachining caninclude ion milling, laser ablation, chemical mechanical polishing(CMP), micro-electrical discharge, micro forging, etc.

Stage 401 also provides a way to connect the actuator defined by magnetassembly 16 and coil 17 to optics assembly 12, so as to effect movementof optics assembly 12 in order to facilitate focusing of the miniaturecamera. More particularly, stage 401 facilitates attachment of magnetassembly 16 to camera optics 12 such that movement of magnet assembly 16in response to current flow through coil 17 results in like movement ofcamera optics 12.

Referring now to FIGS. 6-8, according to an exemplary embodiment of thepresent invention, a magnet assembly 16 comprises a first magnet 601, afirst flux guide 602, a second magnet 603, and a second flux guide 604assembled together into a stack. A non-magnetic, e.g., plastic, holder605, helps to maintain the desired positions of magnets 601 and 603 andflux guides 602 and 602. Magnets 601 and 603, flux guides 602 and 604,and holder 605 can be adhesively bonded to one another. Alternatively,magnets 601 and 603, flux guides 602 and 604, and holder 605 can beattached to one another via the use of detents, fasteners, or by anyother desired method.

A seat 606 can be formed in holder 605 to receive one end of spring 25.As discussed above, spring 25 biases magnet assembly 16, and thus cameraoptics 12 as well, to one extreme of travel.

Referring now to FIG. 9, coil 17 can be attached to housing 20 byadhesive bonding. Coil 17 can alternatively be attached to housing 20 bydetents, fasteners, or by any other desired method. Coil 20 is thusfixedly attached to housing 20 and remains substantially stationary withrespect thereto during operation of the actuator so as to effectmovement of camera optics 12 in order to provide focusing.

Referring now to FIG. 10, magnet assembly 16 is attached to theunderside of stage assembly 14. More particularly, magnet assembly 16 isattached to the underside of stage 401. Magnet assembly 16 can beattached to stage 401 by adhesive bonding. Alternatively, magnetassembly 16 can be attached to stage 401 by detents, fasteners, or byany other desired method.

Thus, magnet assembly 16 is fixedly attached to stage 401 such thatmovement of magnet assembly 16 effects similar movement of stage 401. Inthis manner, camera optics 12, which are attached to stage 401, are alsomoved so as to effect focusing.

Referring now to FIG. 11, lens holder 112 can be screwed into lens mount111 to form camera optics 12 via threads 113 formed upon lens holder 112and threads 114 formed within lens mount 111. The use of threads toattach lens holder 112 to lens mount 111 facilitates adjustment of theoptical elements, e.g., lenses, of lens holder 112 with respect to lensmount 111, so as to tend to position such optical elements for optimumoperation, e.g., focus is optimal at infinity. However, lens holder 112can be attached to lens mount 111 by detents, fasteners, adhesivebonding, or by any other desired method. Lens holder 112 can be attachedto lens mount 111 either before or after lens mount 111, stage assembly14, and magnet assembly 16 are inserted into housing 20 (as shown inFIG. 12).

As shown in FIG. 11, lens mount 111 is attached to the upper surface ofstage 401 and magnet assembly 16 is attached to the underside or lowersurface thereof Thus, movement of magnet assembly 11 results in likemovement of the optical elements of lens holder 112 so as to effectfocusing.

Referring now to FIG. 12, lens mount 111, stage assembly 14, and magnetassembly 16 can be inserted into housing 20. Housing 20 can beconfigured such that a portion of stage assembly 20, such as stationaryportion 1201 thereof, attaches to housing 20. Stationary portion 1201can be attached to housing 20 by adhesive bonding. Alternatively, anyother non-moving portion of stage assembly 14 can be attached to housing20 via detents, fasteners, or by any other desired method. Since anon-moving portion of stage assembly 14 is attached to housing 20, stage401, magnet assembly 16, and lens mount 111 (which contains lens holder112) are free to move along an optical axis of the miniature camera (asindicated by double-headed arrow 406 of FIG. 4).

Referring now to FIGS. 13 and 14, clip 24 can be attached to housing 20to hold bias spring 25 against seat 606 of magnet assembly 16. Clip 24can snap over detents 1301 of housing 20 to effect such attachment.Alternatively, clip 24 can be attached to housing 20 via adhesivebonding, fasteners, or by any other desired method.

Referring now to FIG. 15, lens holder 112 can be attached to lens mount111 after lens mount 111 (along with stage assembly 14 and magnetassembly 16) have been placed into housing 20, if desired.Alternatively, lens holder 112 can be attached to lens mount 11 beforelens mount 11 has been placed into housing 20.

Referring now to FIG. 16, printed circuit board 11 is configured tofacilitate attachment of imaging sensor 13 (FIG. 2) and housing 20thereto. Printed circuit board 11 can also be configured for theattachment of camera electronics thereto. Such camera electronics caninclude a processor and/or controller that facilitates, possibly amongother things, control of the autofocus actuator defined by coil 17 andmagnet assembly 16, as well as facilitates control and readout ofimaging sensor 13.

Referring now to FIG. 17, housing 20 is shown attached to printedcircuit board 20. Imaging sensor 13 is also attached to printed circuitboard 11. Lens holder 112 is shown removed from lens mount 111, so thatimaging sensor 13 can be seen.

Referring now to FIG. 18, electromagnetic interference shield 22 isshown covering housing 20. Electromagnetic interference shield 22 can beattached to housing 20 and/or printed circuit board 11 by adhesivebonding. Alternatively, electromagnetic interference shield 22 can beremovably attached to housing 20 and/or printed circuit board 11 viadetents, fasteners, or any other desired method.

In operation, current flows through coil 17 such that a Lorentz forcegenerated by the cooperation of coil 17 with magnet assembly 16 causesstage 401 to move. Current flow through coil 17 can be controlled by aprocessor, such as a dedicated processor mounted on printed circuitboard 11, to provide autofocus. The processor can alternatively be aprocessor of a personal electronic device, such as a processor of acellular telephone. Stage 401 can be moved so as to position cameraoptics 12 in a manner that effects autofocus according to well knownprinciples. Alternatively, movement of stage 401 can be controlledmanually, such as via a switch of the personal electronics device, so asto enable a user to focus the camera.

In view of the foregoing, one or more embodiments of the presentinvention provide miniature autofocus camera that is suitable for use inpersonal electronic devices, such as cellular telephones. Focusing ofthe camera tends to provide better images, particularly in low lightsituations where a larger aperture is necessary to provide adequatelight or where a higher resolution picture is desirable. The need to usea flash is mitigated by facilitating the use of larger apertures. Sinceless use of a flash is facilitated, the batteries of the personalelectronic device tend to have longer lives.

Embodiments described above illustrate, but do not limit, the invention.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the present invention.Accordingly, the scope of the present invention is fully commensuratewith the following claims and their functional equivalents.

1. A method, comprising: providing a current through a coil; moving alens of a camera, based on the current, to adjust a focus of the camera;and limiting movement of the lens to substantially rectilinear movementalong an optical path of the camera.
 2. The method of claim 1, whereinthe lens is coupled to a stage comprising a magnet, and the movingcomprises moving the magnet in response to the providing of the current.3. The method of claim 1, wherein the magnet comprises a permanentmagnet.
 4. The method of claim 2, wherein the limiting comprisescoupling at least one of the stage and the magnet to the camera througha spring, and the moving comprises moving the lens against a biasimparted to the lens by the spring.
 5. The method of claim 4, whereinthe spring is configured to return the lens to an initial position whenthe current is removed from the coil.
 6. The method of claim 1, whereinthe lens is disposed in a barrel shaped lens holder, and the limitingcomprises limiting movement of the lens holder to substantiallyrectilinear movement along the optical path of the camera.
 7. The methodof claim 6, wherein the limiting further comprises limiting movement ofthe lens holder with a snubber mechanism.
 8. The method of claim 1,wherein the moving comprises moving the lens relative to an imagingsensor, and wherein the method further comprises capturing an imagefocused by the lens on the imaging sensor.
 9. The method of claim 8,further comprising storing the image in the camera.
 10. The method ofclaim 8, further comprising processing the image focused on the imagingsensor with a processor.
 11. A camera, comprising: a coil; circuitry forpassing selectable amounts of current through the coil; and a lensdisposed on a stage comprising a magnet resiliently suspended adjacentto the coil for substantially rectilinear movement relative to the coiland along an optical axis of the lens.
 12. The camera of claim 11,wherein the coil is wound around an axis that is substantiallyperpendicular to a direction of movement of the lens.
 13. The camera ofclaim 11, wherein the lens is mounted on a surface of the stage, and theoptical axis of the lens is disposed substantially parallel to thesurface.
 14. The camera of claim 11, wherein the lens is disposed on aring shaped lens mount, the lens mount is disposed on the stage, and thestage is constrained by a snubber mechanism against all movement exceptfor substantially rectilinear movement along an axis substantiallyparallel to the optical axis of the lens.
 15. The camera of claim 11,wherein the lens comprises at least two lenses disposed parallel to eachother, the at least two lenses having a common optical axis.
 16. Thecamera of claim 15, wherein the at least two lenses are disposed withina barrel shaped lens holder constrained by a snubber mechanism againstall movement except for substantially rectilinear movement along an axissubstantially parallel to the common optical axes of the at least twolenses.
 17. A method, comprising: coupling a lens to a magnet;suspending the magnet adjacent to a coil in such a way that the lens andmagnet move conjointly in response to a passage of a current through thecoil; and constraining movement of the lens and magnet to substantiallyrectilinear movement in a direction substantially parallel to an opticalaxis of the lens.
 18. The method of claim 17, wherein the suspendingcomprises disposing a generally planar surface of the magnet parallel toand spaced apart from a generally planar surface of the coil.
 19. Themethod of claim 17, wherein the constraining comprises utilizing asnubber mechanism.
 20. The method of claim 17, wherein the lens iscoupled to the magnet by at least one of a ring shaped lens mount and/ora barrel shaped lens holder.